Technical Field
The present disclosure relates to cross-linked cyclopolymeric resins having a structure with phospho- and sulfo-pendents with zwitterionic (±) and/or zwitterionic (±) and dianionic groups present in the same repeating unit as well as methods for their synthesis and preparation. Additionally, the present disclosure relates to applications of these cross-linked cyclopolymeric resins as agents for the removal of heavy metals from aqueous solutions.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Heavy metal ion pollution is one of the rising phenomena currently facing humanity due to increasing industrialization, urbanization and other human activities. There are over twenty elements that are classified by the United States Environmental Protection Agency (EPA) as of an environmental and health concern [Akpor, O. and M. Muchie, Remediation of heavy metals in drinking water and wastewater treatment systems: Processes and applications. International Journal of Physical Sciences, 2010. 5(12): p. 1807-1817.—incorporated herein by reference in its entirety]. One such element is nickel (Ni). Nickel (atomic number 28) belongs to group X along with iron in the periodic table. It has a crystalline structure and is a silver-grayish solid with a high polish normally found below the earth's crust (i.e. soils and volcanic rocks). It has an atomic weight of 58.71 g/mol, a specific grabity of 8.9, a melting point (MP) of 1728 K, and a boiling point (BP) of 3186 K [Keng, P.-S., et al., Cheap materials to clean heavy metal polluted waters, in Green Materials for Energy, Products and Depollution. 2013, Springer. p. 335-414.—incorporated herein by reference in its entirety]. Various compounds of nickel have been used for a number of industrial applications which include electroplating, manufacturing of automobile and aircraft parts, batteries, coins, spark plugs, cosmetics, stainless steel, and the industrial scale production of nickel-cadmium batteries.
Like any heavy metal, nickel is toxic and non-biodegradable and usually enters into the environment as a result of anthropogenic activities. An alternative route of entering into the environment is through the weathering of racks and soils and leaching of the minerals [Dojlido, J. and G. A. Best, Chemistry of water and water pollution. 1993: Ellis Horwood Limited.—incorporated herein by reference in its entirety]. Nickel is known to be the cause of “Nickel Itch” (a form of skin irritation and reaction) and is also indicated in other maladies such as asthma, conjunctivitis (pink eye) and inflammatory responses and reactions. Nickel salts when swallowed induce vomiting, and as such act as emetics. A concentration of at least 30 mg can cause changes in vital organs and can reduce function of the muscle, brain, lungs, liver, kidney, etc. and eventually lead to death [VARMA, S., et al., Removal of Nickel from Waste Water Using Graphene Nanocomposite.—incorporated herein by reference in its entirety]. The World Health Organization (WHO) has set the allowable toxicity limits of nickel in the form of Ni (II) as 1.0 mg/m3 (insoluble compounds), 0.1 mg/m3 (soluble compounds), 0.05-0.12 mg/m3 (carbonyl compounds) and 1.0 mg/m3 (nickel sulfide).
A number of technologies are in use to remove pollutants in water including, reverse osmosis, electro dialysis and bioremediation, etc. Adsorption using various adsorbents been receiving increased attention by many researchers as an effective method for the removal of both organic and heavy metal pollutants from water [Kyzas, G. Z. and M. Kostoglou, Green Adsorbents for Wastewaters: A Critical Review. Materials, 2014. 7(1): p. 333-364.; and Aly, H. and A. Daifullah, Potential use of bagasse pith for the treatment of wastewater containing metals. Adsorption science & technology, 1998. 16(1): p. 33-38.; and Daneshvar, N., D. Salari, and S. Aber, Chromium adsorption and Cr (VI) reduction to trivalent chromium in aqueous solutions by soya cake. Journal of Hazardous Materials, 2002. 94(1): p. 49-61.; and Gupta, V. K., et al., Removal of cadmium and nickel from wastewater using bagasse fly ash—a sugar industry waste. Water Research, 2003. 37(16): p. 4038-4044.; and Borhade, A N., et al., Removal of Heavy Metals Cd2+, Pb2+, and Ni2+ From Aqueous Solutions Using Synthesized Azide Cancrinite, Na8[AlSiO4]6(N3)2.4(H2O)4.6. Journal of Chemical & Engineering Data, 2015.; and Boyd, G., A. Adamson, and L. Myers Jr, The exchange adsorption of ions from aqueous solutions by organic zeolites. II. Kinetics1. Journal of the American Chemical Society, 1947. 69(11): p. 2836-2848.—each incorporated herein by reference in its entirety]. Some of these adsorbents have certain limitations such as a longer equilibrium time, a low adsorption capacity, high cost and/or poor recovery [Jiang, J.-Q. and S. Ashekuzzaman, Development of novel inorganic adsorbent for water treatment. Current Opinion in Chemical Engineering, 2012. 1(2): p. 191-199.—incorporated herein by reference in its entirety].
Polymers have been used extensively in wastewater treatment facilities and as such effort has been devoted to the development of novel polymer adsorbents to increase their sorption potential and performance [Ulusoy, U. and R. Akkaya, Adsorptive features of polyacrylamide-apatite composite for Pb2+, UO22+ and Th4+. Journal of hazardous materials, 2009. 163(1): p. 98-108.; and Pan, B., et al., Development of polymeric and polymer-based hybrid adsorbents for pollutants removal from waters. Chemical Engineering Journal, 2009. 151(1): p. 19-29.; and Bai, H., C. Li, and G. Shi, Functional composite materials based on chemically converted graphene. Advanced Materials, 2011. 23(9): p. 1089-1115.; and Ali, S. A., N. Abu-Thabit, and H. A. Al-Muallem, Synthesis and solution properties of a pH-responsive cyclopolymer of zwitterionic ethyl 3-(N,N-diallylammonio) propanephosphonate. Journal of Polymer Science Part A: Polymer Chemistry, 2010. 48(24): p. 5693-5703.; and Ali, S. A. and S. A. Haladu, A novel cross-linked polyzwitterion/anion having pH-responsive carboxylate and sulfonate groups for the removal of Sr2+s from aqueous solution at low concentrations. Reactive and Functional Polymers, 2013. 73(6): p. 796-804.—each incorporated herein by reference in its entirety].
In view of the forgoing, one object of the present disclosure is to provide a cross-linked cyclopolymeric resin. Another object of the present disclosure is to provide a process for producing the cross-linked cyclopolymeric resins featuring phospho- and sulfo-propyl pendents with zwitterionic (±) and/or zwitterionic (±) and dianionic groups present in the same repeating unit (FIG. 1) by the use of Butler's cyclopolymerization protocol. In addition to the cross-linked cyclopolymeric resins and methods for their preparation, the present disclosure further aims to provide methods for efficiently removing (adsorbing) heavy metals, specifically Ni (II) ions, from an aqueous solution by contacting the aqueous media with the cross-linked cyclopolymeric resins described herein.